Crosslinkable bis-imidyl derivatives

ABSTRACT

New crosslinkable bis-imidyl derivatives are described which can be produced by reaction of imidylphthalic acid derivatives, such as maleimidyl-phthalic acid anhydrides, with monomeric, oligomeric or polymeric diamines. The new crosslinkable bis-imidyl derivatives can be used for producing crosslinked polymers which are distinguished, in particular, by their stability to oxidation and to heat.

The present invention relates to new crosslinkable bis-imidylderivatives and to their use for producing crosslinked polymers.

The invention relates to bis-imidyl derivatives of the formula Ia or Ib##STR1## WHEREIN THE X s independently of one another represent hydrogenor, if the radical ##STR2## is in the 4-position of the benzene ring,also --COR₂, the R s and R₂ s independently of one another represent ahydroxyl group, an unsubstituted or substituted phenoxy group, an alkoxygroup having 1-18 carbon atoms, or an --O⁻ M⁺ group,

The R₁ s independently of one another represent a hydroxyl group, anunsubstituted or substituted phenoxy group, an alkoxy group having 1-18carbon atoms, an --O⁻ M⁺ group, or

Two adjacent R₁ s together represent the --O-- grouping, the A sindependently of one another represent a radical of the formula ##STR3##R₃ and R₄ independently of one another represent hydrogen, chlorine,bromine or methyl,

M⁺ represents an alkali metal cation, a trialkylammonium cation having3-24, especially 3-12, carbon atoms or a quaternary ammonium cation,

Q represents --NH-- and Y a bivalent organic radical having at least twocarbon atoms, or --Q--Y--Q-- represents the grouping ##STR4## wherein R₅and R₆ independently of one another represent hydrogen, methyl orphenyl, and to the corresponding cyclised derivatives.

The two A s in formulae Ia and Ib represent preferably identicalradicals as defined, particularly a radical of the formula ##STR5## andespecially a radical of the formula --CH═CH--.

If R, R₁ or R₂ represent substituted phenoxy groups, these are, inparticular, phenoxy groups substituted by nitro groups, alkyl or alkoxygroups having 1 or 2 carbon atoms, or by halogen atoms, especiallychlorine or fluorine, such as the 2-, 3- or 4-nitrophenoxy group, 2,4-or 3,5-dinitrophenoxy group or 3,5-dichlorophenoxy group, thepentachlorophenoxy group, 2-methylphenoxy group or 2-methoxyphenoxygroup.

Alkoxy groups R, R₁ and R₂ can be straight-chain or branched-chain.Examples which may be mentioned are: the methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, tert-butoxy, hexyloxy, octoxy, decyloxy,dodecyloxy, tetradecyloxy and octadecyloxy group. The groups preferredare unsubstituted phenoxy groups or alkoxy groups having 1-12 carbonatoms and especially 1-4 carbon atoms.

If R, R₁ or R₂ represent an --O⁻ M⁺ group, M⁺ represents, for example,the lithium, sodium, potassium, trimethylammonium, triethylammonium,methyl-diethylammonium or tri-n-octylammonium cation. Examples ofquaternary ammonium cation M⁺ are the benzyltrimethylammonium andtetramethylammonium cation. M⁺ preferably represents the sodium cation.

The various R s, R₁ s and R₂ s preferably each represent identicalgroups as defined. The R s preferably each represent a hydroxyl groupand the R₂ s each a hydroxyl group or an alkoxy group having 1-4 carbonatoms. The R₁ s preferably each represent a hydroxyl group; inparticular, however, two adjacent R₁ s together form the --O-- grouping.

Organic radicals denoted by Y or --Q--Y--Q -- can be monomeric,oligomeric or polymeric.

Suitable monomeric organic radicals Y (Q = --NH--) are, in particular,aliphatic radicals having at least two carbon atoms, or cycloaliphatic,carbocyclic-aromatic or heterocyclic-aromatic radicals.

In the case of oligomeric or polymeric organic radicals, Y preferablyrepresents a structural element of the formula II ##STR6## or acorresponding cyclised derivative wherein a represents a number from1-100, preferably a number from 1-60, especially a number from 1-10, andthe individual symbols m, n, Q, Z and Z₁ independently of one anotherrepresent the following:

m and n represent the number 1 or 2,

Q represents --NH-- and

Z represents an aliphatic radical having at least 2 carbon atoms, acycloaliphatic, carbocyclic-aromatic or heterocyclic-aromatic radical,or

Q and Z together with the adjacent Q in the formula Ia or Ib representthe grouping ##STR7## wherein R₅ and R₆ independently of one anotherrepresent hydrogen, methyl or phenyl,

Z₁ represents an aliphatic radical having at least 2 carbon atoms or acycloaliphatic, carbocyclic-aromatic or heterocyclic-aromatic radical,in which the carbonamide groups and carboxyl groups are bound todifferent carbon atoms, and the carboxyl groups, if Z₁ represents acyclic radical and at least one of m and n the number 2, are each in theortho-position with respect to a carbonamide group.

The compounds of the formula Ia or Ib according to the invention and thecorresponding cyclised derivatives can be obtained by a process wherein

(a) a compound of the formula IIIa ##STR8## or

(b) a compound of the formula IIIb ##STR9## or a mixture of twodifferent compounds of the formula IIIa or IIIb, wherein that which hasbeen stated under the formulae Ia and Ib applies in respect of A and X,and the R₁ 's independently of one another represent a hydroxyl group,an unsubtituted or substituted phenoxy group, an alkoxy group having1-18 carbon atoms, or the two R₁ 's together represent the --O--grouping, is reacted, in a molar ratio of at least 2:1, with a compoundof the formula IV

    hq -- y -- qh                                              (iv),

wherein in respect of Q and Y or --Q--Y--Q-- that applies which has beenstated under the formulae Ia and Ib; and the resulting compound of theformula Ia or Ib is optionally subsequently cyclised and/or convertedinto another derivative as defined, i.e. into a compound of the formulaIa or Ib wherein the R s, R₁ s or --COR₂ s have another meaning asdefined.

The conversion into other defined compounds of the formula Ia or Ib canbe performed in a manner known per se, e.g. by hydrolysation ofcompounds with anhydride groupings to the corresponding free acids,reaction of the free acids with alcohols or salt-forming bases to givecompounds of the formula Ia or Ib, wherein R, R₁ or R₂ represent alkoxy,phenoxy or --O⁻ M⁺ groups as defined, or by transesterification.

Defined groups or radicals denoted by Y or Z can be unsubstituted orsubstituted, e.g. by halogen atoms such as fluorine, chlorine orbromine, or by alkyl or alkoxy groups each having 1 to 4 carbon atoms.

In formula II, the individual m, n, Q, Z and Z₁ can have differentmeanings.

Suitable aliphatic radicals Y or Z are, in particular, straight-chain orbranched-chain alkylene groups having 2 to 12 carbon atoms, especiallyunsubstituted alkylene groups having 2-10 carbon atoms, and the alkylenechain can also be interrupted by hetero atoms, such as O, S or N atoms.

Y and Z as a cycloaliphatic radical represent, e.g., the 1,3- or1,4-cyclohexylene group, the 1,4-bis-(methylene)-cyclohexane or thedicyclohexylmethane group.

If Y or Z represents carbocyclic-aromatic radicals, these are preferablymonocyclic radicals, condensed polycyclic radicals or condensed bicyclicaromatic radicals, and in the case of the last-mentioned the aromaticnuclei can be bound together by way of a bridge member.

Examples of suitable bridge members which may be mentioned are:##STR10## wherein Q₁ represents an alkyl group having 1-6, preferably1-4, carbon atoms, or a phenyl group.

Uncondensed bicyclic aromatic radicals Y or Z can also be bound togetherby way of two bridge members, such as two --SO₂ -- groups.

If Y or Z represents a heterocyclic-aromatic radical, such radicals are,in particular, heterocyclic-aromatic 5- or 6-membered rings containingO, N and/or S.

If Z₁ represents an aliphatic radical, these radicals are preferablyunsubstituted, straight-chain or branched-chain saturated alkylenegroups having 1-12 carbon atoms, especially unsubstituted alkylenegroups having 2 to 10 carbon atoms.

Cycloaliphatic radicals denoted by Z₁ are, in particular, 5- or6-membered cycloalkylene groups.

If Z₁ represents a carbocyclic-aromatic radical, this preferablycontains at least one 6-membered ring; such radicals are, in particular,monocyclic or condensed polycyclic radicals or polycyclic radicalshaving several cyclic, condensed or uncondensed systems which can bebound together either direct or by way of bridge members. Suitablebridge members are the groups mentioned in the foregoing in respect of Yand Z.

If Z₁ represents a heterocyclic-aromatic radical, such radicals are, inparticular, 5- or 6-membered heterocyclicaromatic, optionallybenzo-condensed, ring systems which contain O, N and/or S.

Carbocyclic-aromatic or heterocyclic-aromatic radicals represented by Z₁can also be substituted, for example by nitro groups, alkyl groupshaving 1-4 carbon atoms, halogen atoms, especially chlorine, silylgroups, sulphonic acid groups or sulphamoyl groups.

Preferably, Y and the individual Z s where Q = --NH-- independently ofone another represent an unsubstituted alkylene group having 2-12 carbonatoms, or a monocyclic or uncondensed bicyclic aromatic radicalunsubstituted or substituted by halogen atoms, alkyl or alkoxy groupseach having 1-4 carbon atoms, and in the last-mentioned case thearomatic nuclei can be bound together direct or by way of the bridgemember --O--, --CH₂ -- or --SO₂ --.

The individual Z₁ s preferably represent independently of one another anunsubstituted alkylene group having 2-10 carbon atoms, an unsubstitutedmonocyclic aromatic radical, an unsubstituted condensed polycyclicaromatic radical or an uncondensed bicyclic aromatic radical, and in thecase of the last-mentioned, the aromatic nuclei can be bound together byway of the bridge member --O-- or --CO--.

Of the compounds of the formula Ia, those are preferred wherein the tworadicals ##STR11## independently of one another are in the 3- or4-position of the benzene ring, R represents a hydroxyl group and X a--COOalkyl group having 1-4 carbon atoms in the alkyl moiety, especiallyhowever hydrogen; as well as the corresponding cyclised derivatives.

Among the compounds of the formula Ib, those are preferred wherein theR₁ s each represent a hydroxyl group, and particularly such compoundswherein each two adjacent R₁ s together form the --O-- grouping; and thecorresponding cyclised derivatives.

Particularly preferred monomeric bis-imides of the formula Ia and Ib arethose wherein the various symbols have the following meanings:

Q represents --NH--,

Y represents an unsubstituted alkylene group having 2-10 carbon atoms,the 1,3- or 1,4-phenylene group, the 4,4'-diphenylmethane group, the4,4'-diphenylsulphone group or the 4,4'-diphenyl ether group,

A represents a radical ##STR12## and particularly the radical --CH═CH--,X represents a --COOalkyl group having 1-4 carbon atoms in the alkylmoiety, and especially hydrogen,

R represents hydrogen,

R₁ represents hydrogen, and particularly two adjacent R₁ s togetherrepresent the --O-- grouping,

and in formula Ia the two radicals ##STR13## are each in the 3- or4-position of the benzene ring; as well as the corresponding cyclisedderivatives.

Preferred oligomeric or polymeric compounds are those with structuralelements of the formula II wherein Q represents --NH--, Z represents anunsubstituted alkylene group having 2-10 carbon atoms, or acarbocyclic-aromatic radical, particularly the 1,3- or 1,4-phenylenegroup, the 4,4'-diphenyl ether group, the 4,4'-diphenylsulphone group orthe 4,4'-diphenylmethane group, and Z₁ represents an unsubstitutedalkylene group having 2-10 carbon atoms or a carbocyclic-aromaticradical, especially the 1,3- or 1,4-phenylene group, a benzenetriyl orbenzenetetrayl group or the benzophenone ring system; as well as thecorresponding cyclised derivatives.

More particularly preferred are compounds of the formula Ia and Ib withstructural elements of the formula II wherein A, X, R and R₁ have thepreferred meanings stated in the foregoing, Q represents --NH-- and a aninteger from 1-10 and wherein

m and n represent the number 1, Z represents the 1,3- or 1,4-phenylenegroup, the 4,4'-diphenylmethane group or 4,4'-diphenyl ether group, andZ₁ represents an unsubstituted alkylene group having 2-10 carbon atoms,the 1,3- or 1,4-phenylene group, and of Z and Z₁ only one represents the1,4-phenylene group;

m and n represent the number 2, Z represents the 4,4'-diphenylmethanegroup or 4,4'-diphenyl ether group and Z₁ represents a benzenetetraylgroup or the benzophenone ring system;

per structural element a, m represents the number 1 and n the number 2,Z represents the 4,4'-diphenylmethane group or 4,4'-diphenyl ethergroup, and Z₁ represents a benzenetriyl group; as well as thecorresponding cyclised derivatives.

The starting compounds of the formulae IIIa and IIIb can be obtained bya process wherein an amine of the formula V ##STR14## is reacted with ananhydride of the formula VI ##STR15## and the resulting amidocarboxylicacid of the formula VII ##STR16## is subsequently cyclised andoptionally converted into another derivative as defined of the formulaIIIa or into a compound of the formula IIIb.

In the above formulae V to VII, A has the given meaning and X'represents hydrogen or, if the amino group is in the 4-position of thebenzene ring, also -COR₂ ', R" and R₂ ' represent hydroxyl, phenoxy,alkoxy or --O⁻ M⁺ groups corresponding to R or R₂, with however phenoxygroups R" and R₂ ' being free from electronegative substituents such asnitro groups or halogen atoms, and R₂ ' in the case where R" is --OHhaving a meaning other than --O⁻ M⁺, and in the case where R" is --O⁻ M⁺a meaning other than --OH.

Compounds of the formula IIIa wherein R₁ ' and/or R₂ (where X = --COR₂)represent phenoxy groups having electronegative substituents areadvantageously produced by reaction of the corresponding anhydrides oracid anhydrides with suitable alcohols, or by transesterification ofcompounds of the formula IIIa, with R₁ ' and/or R₂ being alkoxy orphenoxy which is free from electronegative substituents.

The reaction of the amines of the formula V with the anhydride of theformula VI can be performed in the melt, in an aqueous oraqueous-organic medium or preferably in an organic medium.

For cyclisation of the amidocarboxylic acid of the formula VII, it ispossible to use customary catalysts such as sodium acetate ortriethylamine, and/or dehydrating agents, e.g. acetic acid anhydride.Simultaneously with the formation of the imide there occurs undercertain circumstances, i.e. depending on the nature of the substituentR", also the formation of the anhydride, e.g. if R" = --OH.

The conversion of the resulting compounds into other defined derivativesof the formula IIIa or into compounds of the formula IIIb is performedin a conventional manner, for example by the methods mentioned in theforegoing.

Acid chlorides of the formula IIIb can be produced, e.g., by reaction ofcompounds of the formula IIIa, wherein X = -COR₂ and R₂ = -OH or --O⁻M⁺, with suitable chlorinating agents, such as thionyl chloride.

The compounds of the formula IV used in the process according to theinvention are known and can be produced in a manner known per se.

The following may be mentioned as examples of monomeric diamines of theformula IV: o-, m- and p-phenylenediamine, diaminotoluenes such as2,4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 2,5-diaminoxylene,1,3-diamino-4-chlorobenzene, 4,4'-diamino-diphenylmethane,4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl thioether,4,4'-diaminodiphenylsulphone, 2,2'-diaminobenzophenone,4,4'-diaminodiphenylurea, 1,8- or 1,5-diaminonaphthalene,2,6-diaminopyridine, 2,4-diaminopyrimidine, 1,4-piperazine,2,4-diamino-s-triazine, di-, tri-, tetra-, hexa-, hepta-, octa-, deca-and dodecamethylenediamine, 2,2-dimethylpropylenediamine,2,5-dimethylhexamethylenediamine, 4,4-dimethylheptamethylenediamine,3-methylheptamethylenediamine, 3-methoxyhexamethylenediamine,2,11-diaminododecane, 2,2,4- and 2,4,4-trimethylhexamethylenediamine,1,2-bis(3-aminopropoxy)-ethane, N,N'-dimethylethylenediamine,N,N'-dimethyl-1,6-diaminohexane, as well as the diamines of the formulaeH₂ N(CH₂)₃ O(CH₂)₂ O-- (CH₂)₃ NH₂ and H₂ N(CH₂)₃ S(CH₂)₃ NH₂, and1,4-diaminocyclohexane.

It is also possible to use mixtures of different monomeric diamines ofthe formula IV.

Compounds of the formula IV wherein Q s each represent --NH--, and Yrepresents a structural element of the formula II, can be obtained in amanner known per se by condensation of di-, tri- or tetracarboxylic acidderivatives of the formula VIII ##STR17## wherein m, n and Z₁ have themeanings given under formula II

and M₁ represents a chlorine atom, a hydroxyl group, an unsubstituted orsubstituted phenoxy group or an alkoxy group having 1-18 carbon atoms,

or M₁, if m and/or n = 2,

together with an M₂ forms the --O-- grouping,

whereby the groups --COM₁ and --COM₂ are bound to different carbonatoms, and the --COM₁ group or groups, if Z₁ represents a cyclic radicaland m and/or n = 2, is or are in the ortho-position with respect to a--COM₂ group, with an excess of a diamine of the formula IX

    hq -- z -- qh                                              (ix)

wherein in respect of Q and Z or --Q--Z--Q-- that applies which isstated under formula I; and possible subsequent cyclisation.

It is also possible to use mixtures of different compounds of theformula VIII and diamines of the formula IX.

If R₁ ' in formula IIIa or M₁ in formula VIII represents unsubstitutedor substituted phenoxy groups or alkoxy groups having 1-18 carbon atoms,preferably 1-12 and especially 1-4 carbon atoms, such groups are, forexample, those mentioned in the foregoing in the discussion of R, R₁ andR₂.

The compounds of the formulae VIII and IX are known per se. As diaminesHQ--Z--QH it is possible to use, for example, compounds of theaforementioned type. Examples of suitable di-, tri- and tetracarboxylicacid derivatives of the formula VIII are: malonic acid, dimethylmalonicacid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacicacid and dodecanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid,hexahydroisophthalic acid, hexahydroterephthalic acid, terephthalicacid, isophthalic acid, 4,4'-dicarboxydiphenylethane,naphthalene-2,6-dicarboxyic acid, thiophene-2,5-dicarboxylic acid andpyridine-2,3-dicarboxylic acid, as well as the corresponding dichloridesand diesters as defined; trimellitic acid-1,2-anhydride-chloride,(1,3-dioxo-benzo[c]oxalane-5-carboxylic acid chloride), trimellitic acidanhydride as well as esters as defined; pyromellitic dianhydride,3,3',4,4'-benzophenone-tetracarboxylic acid dianhydride,2,3,3',4'-benzophenone-tetracarboxylic acid dianhydride,2,2'3,3'-benzophenone-tetracarboxylic acid dianhydride,3,3',4,4'-diphenyl-tetracarboxylic acid dianhydride,bis(2,3-dicarboxyphenyl)-methane-dianhydride,bis(2,5,6-trifluoro-3,4-dicarboxyphenyl)-methane-dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane-dianhydride, bis(3,4-dicarboxyphenyl) etherdianhydride, bis-( 3,4-dicarboxyphenyl)-sulphone-dianhydride,N,N-(3,4-dicarboxyphenyl)-N-methylamine-dianhydride,bis-(3,4-dicarboxyphenyl)-diethylsilanedianhydride, 2,3,6,7- and1,2,5,6-naphthalene-tetracarboxylic acid-dianhydride,2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid-dianhydride,thiophene-2,3,4,5-tetracarboxylic acid-dianhydride,pyrazine-2,3,5,6-tetracarboxylic acid-dianhydride,pyridine-2,3,5,6-tetracarboxylic acid-dianhydride.

The dicarboxylic acid derivatives used are preferably dicarboxylic aciddichlorides.

The condensation of the compounds of the formula IIIa, IIIb and VIIIwith the compounds of the formula IV or with the diamines HQ--Z--QH isperformed in a manner known per se, advantageously at temperatures ofabout -50° C. to +300° C. The condensation can be perfomed in the meltor preferably in an inert organic solvent or in a solvent mixture. Forthe condensation in solution, temperatures of -20° C. to +50° C. arepreferred. For the reaction of the compounds of the formulae IIIa andIIIb with the compounds of the formula IV, the addition of knownpolymerisation inhibitors, such as hydroquinones, brenzcatechin,cresoles, e.g. ditert.butylcresole, can under certain circumstances beadvantageous.

As organic solvents it is possible to use, e.g.:

optionally chlorinated aromatic hydrocarbons, such as benzene, toluene,xylenes and chlorobenzene;

chlorinated aliphatic hydrocarbons, such as methylene chloride,chloroform, tetrachloroethane and tetrachloroethylene;

aliphatic and cycloaliphatic ketones, such as acetone, methyl ethylketone, cyclopentanone and cyclohexanone;

cyclic ethers, such as tetrahydrofuran, tetrahydropyrane and dioxane;

cyclic amides, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidoneand N-methyl-ε-caprolactam;

N,n-dialkylamides of aliphatic monocarboxylic acids having 1-3 carbonatoms in the acid moiety, such as N,N-dimethylformamide,N,N-dimethylacetamide, N,N-diethylacetamide andN,N-dimethylmethoxyacetamide;

ethylene glycol monoalkyl ether and ethylene glycol dialkyl ethers eachhaving 1-4 carbon atoms in the alkyl moieties, such as ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, ethylene glycolmonoisopropyl ether and ethylene glycol mono-n-.butyl ether, ethyleneglycol dimethyl ether and ethylene glycol diethyl ether;

alkyl esters of aliphatic monocarboxylic acids having a total of 2-6carbon atoms, such as formic acid or acetic acid methyl ester, formic oracetic acid ethyl ester and formic acid or acetic acid n-butyl ester.

hexamethylphosphoric acid triamide (hexametapol);

N,n,n',n'-tetramethylurea;

tetrahydrothiophene dioxide (sulpholane);

dialkyl sulphoxides, such as dimethyl and diethyl sulphoxide.

It is also possible to use mixtures of such solvents.

Preferred solvents are N,N-dialkylamides of aliphatic monocarboxylicacids having 1-3 carbon atoms in the acid moiety, especiallyN,N-dimethylacetamide, as well as cyclic amides, such asN-methyl-pyrrolidone.

The hydrochloric acid forming on condensation or polycondensation ofcompounds of the formula IIIb or VIII, wherein M₁ represents chlorine,with the diamines HQ--Y--QH or HQ--Z--QH can be removed byneutralisation with basic substances such as calcium hydroxide ortriethylamine, or by reaction with an epoxide compound such as ethyleneoxide or propylene oxide, and by washing out with suitable solvents,e.g. water.

The condensation reactions are advantageously performed with theexclusion of moisture, e.g. in an inert gas atmosphere, such asnitrogen.

The compounds of the formulae IIIa and IIIb are reacted with thecompounds of the formula IV in a molar ratio of at least 2:1. If thecompound of the formula IV is a monomeric diamine, this diamine isadvantageously used in a stoichiometric amount or slightly lesseramount. For the reaction with oligomers or polymers of the formula IVwhich contain terminal amino groups, the reactants are used preferablyin a stoichiometric amount.

In the case of the eventual cyclisation of the compounds of the formulaIa or Ib or IV resulting on condensation, there occurs imide formation,and with compounds of the formula Ib optionally also anhydrideformation. Cyclisation is performed, in a manner known per se,chemically or preferably thermally.

Chemical cyclisation is advantageously performed by treatment with adehydrating agent alone or in admixture with a tertiary amine. Suitablefor the purpose are, e.g., acetic acid anhydride, propionic acidanhydride and dicyclohexylcarbodiimide, or mixtures of acetic acidanhydride and triethylamine.

Thermal cyclisation is performed by heating at temperatures of about50°-250° C., preferably about 100°-150° C., and optionally with theaddition of a solvent and/or of a water-entrainer such as xylenes ortoluene. At temperatures above about 150° C. there also occurs, at leastpartially, a crosslinking.

The crosslinking of the compounds of the formula Ia or Ib is likewiseperformed in a manner known per se, chemically, thermally or under theinfluence of electromagnetic waves, particularly light.

Chemical crosslinking is generally carried out at temperatures of about50° to 250° C. and in the presence of known radical initiators, such asinorganic and organic peroxides or azo compounds, e.g. hydrogenperoxide, tert. butylhydroxy peroxide, peracetic acid, benzoyl peroxide,tert.butylperbenzoate, cumolhydroperoxide, dicumyl peroxide andα,α'-azo-iso-butyronitrile.

Thermal crosslinking is advantageously performed by heating attemperatures up to about 350° C., preferably 150°-250° C., andoptionally in the presence of radical initiators of the aforementionedtype.

For crosslinking under the influence of electromagnetic waves, suitablecompounds are, in particular, those of the formula Ia or Ib wherein Arepresents a radical of the formula ##STR18## Crosslinking can beperformed, e.g., by means of irradiation with X rays or UV light, andoptionally in the presence of sensitisers, such as benzene,1,4-diacetylbenzene, phenol, benzonitrile, acetophenone, benzophenone,benzaldehyde, di-isopropyl ketone and fluorene.

The crosslinkable compounds of the formula Ia and Ib according to theinvention and the corresponding cyclised derivatives are valuablestarting products for producing crosslinked polymers having goodmechanical, electrical and/or thermal properties. The crosslinkedpolymers obtainable therewith are distinguished in particular by theirstability to oxidation and to heat. Compared with known bis-imides,especially bis-maleimides such asN,N'-4,4'-diphenyl-methane-bis-maleimide, the bis-imides according tothe invention are distinguished also by their easier availability inthat the corresponding amide acids, in contrast to known bis-maleamideacids, can be cyclised, and possibly simultaneously crosslinked, notonly chemically but also very readily thermally, i.e. by mere heating.

Compared with the mentioned bis-maleamide acids, the non-cyclisedcompounds of the formula Ia and Ib have in some cases an improvedsolubility in organic solvents, such as ethylene glycol monoalkyl etherand ethylene glycol dialkyl ether, e.g. ethylene glycol monomethylether.

The compounds of the formula Ia and Ib according to the invention areobtained on cyclisation generally in the form of white to yellowpowders, and for the most part are soluble in customary organicsolvents, such as methylene chloride, chloroform, dioxane,N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

EXAMPLE 1 ##STR19##

In a sulphonating flask, 91.89 g (0.378 mole) of 3-maleimidyl-phthalicacid anhydride is dissolved, in a nitrogen atmosphere, in 343 ml ofanhydrous N,N-dimethylacetamide (DMA), and the solution is cooled to0°-5° C. An addition is then made dropwise, with stirring, of a solutionof 35.68 g (0.18 mole) of 4,4'-diaminodiphenylmethane in 200 ml of DMA,and after completion of the addition the reaction mixture is stirred at20°-25° C. for a further 2 hours. There is then added 132 ml (1.44moles) of acetic acid anhydride, and the solution is heated, withstirring, for 2 hours at 80° C. After cooling to about 20°-25° C., thereaction product is precipitated with water. The precipitate is filteredoff, washed repeatedly with water, and dried for 20 hours at 80° C. in avacuum chamber. The reaction product is then boiled in about the tenfoldamount by weight of ethanol for 20 minutes and subsequently filteredhot. On drying at 80° C. under high vacuum, there is obtained 107 g ofbis-3-maleiimidylphthalimide of the above formula in the form ofslightly yellowish powder; m.p. 190°-210° C., yield 91% of theory.

Analysis for C₃₇ H₂₀ O₈ N₄ (molecular weight 648.59): calculated: C,68.52%; H, 3.11%; N, 8.64%. found: C, 68.7%; H, 3.3%; N, 8.4%.

The 3-maleimidylphthalic acid anhydride used in the above Example isproduced, in a manner known per se, by reaction of 3-aminophthalic acidwith maleic acid anhydride and cyclisation of the resulting3-maleamidylphthalic acid with anhydrous sodium acetate and aceticanhydride (see U.S. 3,979,393).

EXAMPLE 2

In a nitrogen atmosphere in a sulphonating flask, 43.76 g (0.18 mole) of3-maleimidyl-phthalic acid anhydride is dissolved in 200 ml of anhydrousDMA, and the solution is cooled to 0°-5° C. To the solution obtained isadded dropwise, with stirring, a solution of 17.84 g (0.09 mole) of4,4'-diaminodiphenylmethane in 96 ml of DMA. After the addition iscompleted, the reaction mixture is stirred at 20°-25° C. for 30 minutes.There is then added 140 ml of anhydrous xylene and the sulphonatingflask is provided with a water separator. The reaction solution isrefluxed until no further water is separated. The xylene is subsequentlydistilled off and the reaction product is precipitated in water. Theresulting precipitate is filtered off, washed several times firstly withwater and then with ethanol and dried in a vacuum oven at 80° C. for 32hours. There is obtained 50 g of bis-3-maleimidylphthalimide of theformula given in Example 1 in the form of a yellowish powder; m.p.190°-210° C., yield 86% of theory.

Analysis for C₃₇ H₂₀ O₈ N₄ (molecular weight 648.59): calculated: C,68.52%; H, 3.11%; N, 8.64%. found: C, 68.24%; H, 3.40%; N, 8.61%.

EXAMPLE 3 ##STR20##

By the procedure described in Example 1, 15.31 g (0.063 mole) of4-maleimidyl-phthalic acid anhydride is reacted with 5.94 g (0.03 mole)of 4,4'-diaminodiphenylmethane in 200 ml of DMA. After precipitation anddrying, there is obtained 12.15 g of the bis-maleimidylphthalimide ofthe above formula in the form of yellow powder; m.p. 180°-200° C., yield62% of theory.

The 4-maleimidylphthalic acid anhydride used as starting product isproduced according to Example 3 of U.S. Pat. No. 3,979,393.

EXAMPLE 4 ##STR21##

15.31 g (0.063 mole) of a 1:1 mixture of 3-maleimidylphthalic acidanhydride and 4-maleimidyl-phthalic acid anhydride is reacted with 5.94g (0.03 mole) of 4,4'-diaminodiphenylmethane in 200 ml of DMA using theprocedure described in Example 1. After precipitation, washing anddrying, there is obtained 12.15 g of a mixture of isomericbis-maleimidylphthalimides as yellow powder; m.p. 180°-210° C., yield63% of theory.

EXAMPLE 5

For processing by the compression process, thebis-3-maleimidylphthalimide produced according to Example 2 isintroduced into a compression mould, preheated to 250° C., for standardtest bars, and moulded at this temperature for 1 hour under a pressureof 250 kp/cm². After removal from the mould, the resulting transparentbars are annealed in a furnace at 240° C. for 16 hours. Solid, slightlybrittle moulded specimens are obtained.

EXAMPLE 6

24.31 g (0.10 mole) of 3-maleimidyl-phthalic acid anhydride is dissolvedin 200 ml of methylene chloride and the solution is cooled to 0° C. Anaddition is then made dropwise, with stirring, of a solution of 9.92 g(0.05 mole) of 4,4'-diaminodiphenylmethane in 50 ml of methylenechloride, whereupon a voluminous precipitate is formed. The reactionmixture is stirred at 20°-25° C. for one hour and subsequentlyconcentrated in vacuo to dryness. The residue obtained is heated under aslight vacuum at 180° C. for 1 hour and then finely pulverised to yield30.2 g of a pre-polymer from the bis-3-maleimidylphthalimide, describedin Example 1, in powder form. For processing by the compression process,the powder is introduced into a compression mould, preheated to 260° C.,for standard test bars, and moulded at this temperature for 1 hour undera pressure of 250 kp/cm². On removal from the mould are obtained wellconsolidated, slightly brittle moulded specimens, the flexural strengthof which was not decreased after ageing for 300 hours at 240° C. in air.

EXAMPLE 7

7.92 g (0.04 mole) of 4,4'-diaminodiphenylmethane is dissolved in 50 mlof anhydrous DMA in a nitrogen atmosphere in a sulphonating flask, andthe solution is then cooled to 0°-5° C. An addition is made dropwise,with stirring, of a solution of 6.44 g (0.02 mole) of 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, the manner ofaddition being such that the temperature of the reaction mixture doesnot exceed 15° C. After completion of the addition, the reaction mixtureis stirred at 20°-25° C. for 2 hours; it is then cooled to 5° C. and asolution of 9.62 g (0.04 mole) of 4-maleimidyl-phthalic acid anhydrideis added dropwise. After 1.5 hours' stirring at 20°-25° C., 100 ml ofacetic acid anhydride is added, and the reaction solution is stirred at20°-25° C. for a further 16 hours. It is then poured into water, theprecipitated product is filtered off and washed several times withwater. After filtration with suction and drying in a vacuum oven at 80°C. for 24 hours, there is obtained 20.8 g of a crosslinkable polyimideoligomer in the form of a yellow powder.

For processing by the compression process, the above powder isintroduced into a compression mould, preheated to 250° C., for standardtest bars, and moulded at this temperature for one hour under a pressureof 500 kp/cm². After removal from the mould, the moulded specimens areannealed at 200° C. in a furnace for 16 hours. Well consolidated mouldedspecimens are obtained.

EXAMPLE 8

11.90 g (0.06 mole) of 4,4'-diaminodiphenylmethane is dissolved in 160ml of anhydrous DMA in a nitrogen atmosphere in a sulphonating flask,and the solution is cooled to -15° to -20° C. 8.42 g (0.04 mole) oftrimellitic acid anhydride chloride in solid form is added portionwise,with stirring, in such a manner that the temperature of the reactionsolution does not exceed -15° C. The solution is then stirred at -15° C.for 30 minutes and afterwards at 20°-25° C. for a further hour. Anaddition is subsequently made dropwise of 4.04 g (0.04 mole) oftriethylamine in 35 ml of DMA, and a fine precipitate is formed. Thereaction mixture is stirred for a further hour at 20°-25° C., and 9.72 g(0.04 mole) of a 1:1 mixture of 3- and 4-maleimidyl-phthalic acidanhydride is then added portionwise at 15°-20° C. After one hour'sstirring at 20°-25° C., the precipitated triethylamine hydrochloride isseparated by filtration, and 75 ml of anhydrous xylene is added to thereaction solution. The solution is then refluxed until, with the aid ofa water separator, no further water can be separated. The xylene isdistilled off, and the solution after cooling is precipitated in water.The precipitate obtained is filtered off, washed with water andsubsequently dried at 80° C. for 40 hours in a vacuum chamber to yield24.6 g of an oligoamideimide containing terminal maleimidylphthalimidegroups, in the form of a yellow powder.

A compression mould, preheated to 250° C., for standard test bars isfilled with the above oligoamide-imide. The powder is then moulded at260° C. under a pressure of 500 kp/cm² for 40 minutes. The resultingmoulded specimens are removed from the mould and annealed at 240° C. for16 hours to obtain transparent solid moulded specimens.

EXAMPLE 9

By a procedure analogous to that described in Example 8, 19.82 g (0.10mole) of 4,4'-diaminodiphenylmethane, 16.84 g (0.08 mole) of trimelliticacid anhydride chloride, 8.08 g (0.08 mole) of triethylamine and 9.72 g(0.04 mole) of 3-maleimidyl-phthalic acid anhydride are reacted in 330ml of anhydrous DMA, and the precipitated triethylamine hydrochloride isremoved. To the filtered reaction solution is then added dropwise, withstirring, 200 ml of acetic acid anhydride, and stirring is maintained at20°-25° C. for 16 hours. The reaction solution is subsequently pouredinto water, the precipitated product is separated, washed with water anddried in a vacuum drying chamber for 16 hours at 80° C. and 130° C.,respectively. There is obtained 37.2 g of a still crosslinkableoligoamide-imide in the form of a yellow powder.

For processing by the compression process, the oligoamide-imide powderobtained is well mixed with 2 percent by weight of dicumyl peroxide; themixture is introduced into a compression mould for circular discs,preheated to 220° C., and moulded under a pressure of 225 kp/cm² for 15minutes at 225° C. and for 5 minutes at 260° C. A transparent dischaving a good mechanical strength is obtained.

If the oligoamide-imide is introduced without additives into thecompression mould and moulded at 265° C. under a pressure of 225 kp/cm²for 10 minutes, there is likewise obtained a transparent disc from thecrosslinked polyamide-imide.

EXAMPLE 10

4.32 g (0.04 mole) of m-phenylenediamine is dissolved in 100 ml ofanhydrous DMA in a nitrogen atmosphere in a sulphonating flask, and thesolution is cooled to -15° C. 6.09 g (0.03 mole) of isophthalic aciddichloride is added portionwise, with stirring, in such a manner thatthe temperature of the reaction mixture does not exceed -10° C. Thereaction solution is then stirred at -15° C. for 30 minutes andsubsequently at 20°-25° C. for a further hour. An addition is then madedropwise of 6.07 g (0.06 mole) of triethylamine in 40 ml of anhydrousDMA, with a white precipitate being formed. The reaction mixture isstirred for a further hour at 20°-25° C., and there is then addedportionwise, at 15°-20° C., 4.86 g (0.02 mole) of a 1:1 mixture of 3-and 4-maleimidyl-phthalic acid anhydride. After stirring for 1 hour at20°-25° C., the precipitated triethylamine hydrochloride is filteredoff. An addition is then made dropwise, with stirring, of 90 ml ofacetic acid anhydride. The reaction solution is stirred for 16 hours at20°-25° C., and is then poured into water. The precipitated product isfiltered off, washed with water and dried in a vacuum drying chamber at80° C. for 40 hours. 11.5 g of a crosslinkable oligoamide in the form ofa slightly yellowish powder is obtained.

The above oligoamide powder is introduced into a compression mould,preheated to 220° C., for circular discs and then moulded at thistemperature under a pressure of 675 kp/cm² for 30 minutes. After removalfrom the mould, transparent, slightly brittle moulded specimens areobtained.

EXAMPLE 11

11.92 g (0.048 mole) of 4,4'-diaminodiphenylsulphone, 8.93 g (0.044mole) of isophthalic acid dichloride, 8.90 g (0.088 mole) oftriethylamine and 1.93 g (0.008 mole) of 3-maleimidyl-phthalic acidanhydride are reacted in 215 ml of anhydrous DMA using the proceduredescribed in Example 10. The triethylamine hydrochloride is filtered offand the reaction solution is poured directly into water. Theprecipitated product is washed with water and dried in a vacuum dryingchamber for 40 hours at 80° C. and for 3 hours at 150° C. to leave 16.6g of a crosslinkable polyamide in the form of a yellowish powder.

The above polyamide powder is introduced into a compression mould,heated to 300° C., for circular discs and then moulded at thistemperature under a pressure of 225 kp/cm² for 30 minutes to obtain wellconsolidated transparent discs.

EXAMPLE 12

4.32 g (0.04 mole) of m-phenylenediamine is dissolved in 100 ml ofanhydrous DMA in a nitrogen atmosphere in a sulphonating flask, and thesolution is cooled to -15° to -20° C. Whilst stirring is maintained,8.37 g (0.035 mole) of sebacic acid dichloride is added dropwise in sucha manner that the temperature of the reaction mixture does not exceed-15° C. The reaction mixture is then stirred for 1 hour at 20°-25° C.With cooling again to -15° C., an addition is made dropwise of 7.08 g(0.07 mole) of triethylamine in 14 ml of DMA, whereupon a whiteprecipitate is formed. The reaction mixture is stirred at 20°-25° C. fora further hour, and the precipitated triethylamine hydrochloride isremoved by filtration. The precipitate is washed with 30 ml of DMA, andto the filtrate at 0° C. is added 2.43 g (0.01 mole) of3-maleimidyl-phthalic acid anhydride. The reaction solution obtained isstirred for 2 hours at 20°-25° C.; 80 ml of acetic acid anhydride isthen added dropwise, the reaction solution is stirred for 16 hours at20°-25° C., and finally poured into water. The precipitated product isfiltered off, washed several times with water and dried in a vacuumdrying chamber for 16 hours at 80° C./20 torr and for 16 hours at 80°C./10⁻¹ torr to obtain 11.1 g of a crosslinkable oligoamide in the formof a slightly yellowish powder.

For processing by the compression process, the above oligoamide powderis heated for 80 minutes at 165° C./10⁻¹ torr; it is then introducedinto a compression mould, preheated to 195° C., for circular discs, andmoulded at this temperature for 90 minutes under a pressure of 325kp/cm². After removal from the mould, the moulded specimens are annealedat 150° C. for 16 hours. Solid transparent discs are obtained.

EXAMPLE 13

In a nitrogen atmosphere in a sulphonating flask, 11.99 g (0.06 mole) of4,4'-diaminodiphenylmethane is dissolved in 350 ml of anhydrous DMA, andthe solution is cooled to 0°-5° C. While stirring is maintained, 12.89 g(0.04 mole) of 3,3', 4,4'-benzophenone-tetracarboxylic acid dianhydrideis added portionwise in such a manner that the temperature does notexceed 5° C. After completion of the addition, the reaction mixture isstirred for 1 hour at 20°-25° C.; it is then cooled to 5° C. and 12.36 g(0.04 mole) of 3-nadicimidylphthalic acid anhydride in solid form isadded. After 1 hour's stirring at 20°-25° C., 100 ml of anhydroustoluene is added, and the reaction solution is refluxed until, with theaid of a water separator, no further water is separated therefrom. Thetoluene is subsequently distilled off and the reaction solution ispoured into water. The resulting precipitate is filtered, washed severaltimes with water and dried in a vacuum oven at 80° C. for 32 hours toyield 25.3 g of a crosslinkable polyimide oligomer in the form of ayellowish powder.

For processing by the compression process, the above oligomer is firstlyheated at 300° C. for 5 minutes, then again finely pulverised andintroduced into a compression mould, heated to 320° C., for circulardiscs. The powder is subsequently moulded at this temperature for 45minutes under a pressure of 100 kp/cm² to obtain transparent solidmoulded specimens.

The 3-nadicimidylphthalic acid anhydride[3-(bicyclo[1.2.2]hept-5-ene-2,3-dicarboxylic acid imidyl)-phthalic acidanhydride] is produced, in a manner known per se, by reaction of3-aminophthalic acid with nadic acid anhydride and cyclisation of theresulting 3-nadicamidyl-phthalic acid with anhydrous sodium acetate andacetic anhydride (see DOS 2,459,673).

EXAMPLE 14

7.93 g (0.04 mole) of 4,4'-diaminodiphenylmethane, 4.36 g (0.02 mole) ofpyromellitic acid dianhydride and 12.36 g (0.04 mole) of a 1:1 mixtureof 3- and 4-nadicimidylphthalic acid anhydride are reacted in 235 ml ofanhydrous DMA and 80 ml of toluene by the procedure described in Example13. There is obtained 19.97 g of a slightly yellowish powder which, forprocessing, is introduced into a compression mould, heated to 295° C.,for circular discs. The powder is then moulded at this temperature for 5minutes under contact pressure and for 60 minutes under a pressure of100 kp/cm² to obtain well consolidated discs.

EXAMPLE 15

In a nitrogen atmosphere in a sulphonating flask, 15.4 g (0.05 mole) of3-nadicimidylphthalic acid anhydride is dissolved in 195 ml of DMA, andreacted with 5.0 g (0.025 mole) of 4,4'-diaminodiphenyl ether and 50 mlof toluene using the procedure described in Example 13. There isobtained 16.55 g of bis-imide of the formula ##STR22## as a slightlyyellowish powder which softens under pressure at 200° C.

EXAMPLE 16

By the procedure described in Example 15, 15.45 g (0.05 mole) of a 1:1mixture of 3- and 4-nadicimidylphthalic acid anhydride is reacted with2.90 g (0.025 mole) of 1,6-diaminohexane in 175 ml of anhydrous DMA and80 ml of toluene. There is obtained 11.67 g of bis-imide of the formula##STR23## in the form of a yellowish powder which softens at 120° C.under pressure.

EXAMPLE 17

By the procedure described in Example 12, 1.95 g (0.018 mole) ofm-phenylenediamine, 3.59 g (0.015 mole) of sebacic acid dichloride,3.303 g (0.03 mole) of triethylamine and 1.63 g (0.006 mole) of3-(2,3-dimethylmaleimidyl)-phthalic acid anhydride are reacted in 50 mlof anhydrous DMA. The resulting 15% solution is poured onto aluminiumplates and dried as follows: 16 hours at 100° C./20 torr, 1 hour at 120°C./20 torr, 1 hour at 140° C./20 torr, 2 hours at 150° C./20 torr, 16hours at 150° C./10⁻¹ torr and 1 hour at 200° C./10⁻¹ torr. Thespecimens are then irradiated for 2 hours with a 400 watt UV lamp. Atransparent, slightly brittle coating is obtained.

The 3-(2,3-dimethylmaleimidyl)-phthalic acid anhydride used in the aboveExample can be produced, in a manner known per se, by reaction of3-aminophthalic acid with 2,3-dimethylmaleic acid anhydride, andcyclisation of the resulting 3-(2,3-dimethylmaleamidyl)-phthalic acid,e.g. with acetic acid ethyl ester.

EXAMPLE 18

By the procedure described in Example 10, 3.46 g (0.032 mole) ofm-phenylenediamine, 4.87 g (0.024 mole) of isophthalic acid dichloride,4.85 g (0.048 mole) of triethylamine and 5.04 g (0.016 mole) of4-maleimidyltrimellitic acid anhydride ethyl ester are reacted in 130 mlof anhydrous DMA. After imidisation, with 60 ml of acetic acidanhydride, precipitation in water, washing and drying, there is obtained6.25 g of bis-imidyl ester in the form of a yellowish powder.

For processing by hot compression moulding, the above powder isintroduced into a compression mould, preheated to 265° C., for circulardiscs, and moulded at this temperature for 30 minutes under a pressureof 100 kp/cm². Well consolidated discs are obtained.

The 5-maleimidyltrimellitic acid anhydride ethyl ester used in the aboveExample can be produced as follows:

61.33 g (0.24 mole) of 4-nitrotrimellitic acid anhydride chloride(obtained by chlorination of 4-nitrotrimellitic acid anhydride withthionyl chloride) is dissolved in 120 ml of dioxane, and 13.94 ml (0.24mole) of ethanol is added with stirring. The reaction mixture is stirredfor 12 hours at 25° C., then heated for 1 hour at 80° C. and finallyconcentrated by evaporation to dryness. The residue is dissolved in 180ml of dioxane; 100 ml of water is added dropwise and, after one hour,the solution is concentrated by evaporation to dryness. The residueobtained is finely suspended in 100 ml of benzene, filtered off withsuction, and dried at 80° C. in a drying chamber to obtain 60.5 g of4-nitrotrimellitic acid ethyl ester, m.p. 189°-191° C. 65.13 g (0.23mole) of this ester is dissolved in 150 ml of dioxane and hydrogenatedin the presence of 6.5 g of a palladium charcoal catalyst, containing 5%by weight of Pd, at 30° C. The reaction solution is filtered; 27 g ofmaleic anhydride is added and the solution is left to stand for 12 hoursat 20°-25° C. The solution is then concentrated by evaporation at40°-60° C., and to the oily residue is added, with stirring, 250 ml ofdiethyl ether. The 4-maleamidyl-trimellitic acid ethyl ester, whichprecipitates as a fine white substance, is filtered off with suction anddried at 50° C. in a drying chamber. There is obtained 76.7 g of thestated ester; m.p. 142°-144° C. 58 g (0.165 mole) of the4-maleamidyltrimellitic acid ethyl ester is slowly introduced at 80° C.,in the course of 15 minutes, into a mixture of 65 ml of acetic anhydrideand 14.5 g of sodium acetate. The reaction mixture is stirred for 3hours at this temperature; it is then concentrated by evaporation todryness and the residue is extracted three times with 200 ml of tolueneeach time. The combined toluene extracts are concentrated by evaporationto dryness. The solid residue is dissolved hot in 100 ml of toluene andthen filtered. The 4-maleimidyl-trimellitic acid anhydride ethyl esterthat has crystallised out on cooling of the solution is filtered offwith suction and dried in a drying chamber at 70° C. to obtain 39.6 g of4-maleimidyl-trimellitic acid anhydride ethyl ester, m.p. 178°-179° C.

EXAMPLE 19

7.93 g (0.04 mole) of 4,4'-diaminodiphenylmethane is dissolved in 130 mlof anhydrous DMA in a nitrogen atmosphere in a sulphonating flask, andthe solution is cooled to -15° C. With stirring, 6.49 g (0.032 mole) ofisophthalic acid dichloride is added portionwise so that the temperatureof the reaction solution does not exceed -10° C. The reaction solutionis then further stirred for 30 minutes at -15° C. and subsequently for 1hour at 20°-25° C. The reaction solution is thereupon again cooled to-15° C., and a solution of 8.09 g (0.08 mole) of triethylamine in 50 mlof DMA is added dropwise with the result that a white precipitate isformed. The reaction mixture is stirred for 1 hour at 20°-25° C.; it isagain cooled to -15° C. and 4.66 g (0.016 mole) of4-maleimidyl-trimellitic acid anhydride chloride is added. After onehour's stirring at 20°-25° C., the reaction mixture is precipitated inmethanol; the precipitate is filtered off, washed with water, and driedin a vacuum oven at 80° C. for 36 hours to obtain 13.18 g ofcrosslinkable oligomer in the form of a yellowish powder.

This powder is introduced into a compression mould, heated at 265° C.,for circular discs and at this temperature is moulded for 30 minutesunder a pressure of 450 kp/cm². On removal from the mould, tough solidmoulded specimens are obtained.

The 4-maleimidyl-trimellitic acid anhydride chloride used in the aboveExample is produced as follows:

102 g (0.4 mole) of 4-nitrotrimellitic acid (obtained by nitration oftrimellitic acid anhydride with H₂ SO₄ /HNO₃) is hydrogenated in thepresence of 10 g of a palladium charcoal catalyst, containing 5% byweight of Pd, at 30° C. in 1000 ml of dioxane. The reaction solution isfiltered, and 46.8 g (0.48 mole) of maleic acid anhydride is then added.The reaction mixture is allowed to stand for 12 hours at 20°-25° C. andis subsequently concentrated to dryness at 60° C. in a rotaryevaporator. The residue is heated to boiling twice, with stirring, with400 ml of acetic acid ethyl ester each time; it is then filtered offwith suction and dried at 80° C./100 torr for 24 hours to obtain 105 gof 4-maleamidyl-trimellitic acid.

32.3 g (0.1 mole) of the 4-maleamidyl-trimellitic acid is mixed with 1.6g of anhydrous sodium acetate and 83 ml of acetic anhydride, and heatedat 80° C. for 30 minutes. The formed solution is concentrated byevaporation to dryness and subsequently dried at 50° C./0.05 torr. 200ml of thionyl chloride is added to the residue and the reaction mixtureis heated at 80° C. for 2.5 hours. It is then concentrated to drynessand 150 ml of benzene is added; the reaction mixture is filtered, thefiltrate is concentrated by evaporation and finally dried at 80° C./0.1torr. After washing with cyclohexane and benzene and then drying, 18.31g of crystalline 4-maleimidyl-trimellitic acid anhydride chloride, m.p.143°-144° C., is obtained.

EXAMPLE 20

3.78 g (0.012 mole) of 4-maleimidyl-trimellitic acid anhydride ethylester and 1.19 g (0.006 mole) of 4,4'-diaminodiphenylmethane are reactedin 47 ml of anhydrous DMA using the procedure described in Example 1.After imidisation with 20 ml of acetic acid anhydride, precipitation,washing and drying, 3.86 g of bis-imidyl ester of the formula ##STR24##is obtained in the form of a yellow powder.

For processing by compression moulding, the above powder is firstlysubjected to a preliminary chain-lengthening reaction for 30 minutes at200° C., again pulverised and then introduced into a compression mould,heated to 200° C., for circular discs. The powder is moulded under apressure of 100 kp/cm² for 50 minutes, with the temperature rising from200° C. to 250° C. Transparent solid discs are obtained.

We claim:
 1. A crosslinkable compound of the formula ##STR25## whereinthe Xs independently of one another represent hydrogen, or if theradical ##STR26## is in the 4-position of the benzene ring, also --COR₂,the R₂ s independently of one another represent hydroxyl, phenoxy;phenoxy substituted by one or two nitro groups, by one alkyl of 1 to 2carbon atoms, by one alkoxy of 1 to 2 carbon atoms or by two or fivehalogen atoms; alkoxy of 1 to 18 carbon atoms or an O⁻ M⁺ group,the A sindependently of one another represent a radical of the formula##STR27## ##STR28## R₃ and R₄ independently of one another representhydrogen, chlorine, bromine or methyl, M⁺ represents an alkali metalcation, a trialkylammonium cation having 3 to 24 carbon atoms or aquaternary ammonium cation, and Y represents alkylene of 2 to 10 carbonatoms, 1,3-phenylene, 1,4-phenylene, the 4,4'-diphenylmethane group, the4,4'-diphenylsulfone group or the 4,4'-diphenyl ether group.
 2. Acrosslinkable compound according to claim 1 of formula Ia' wherein thetwo radicals ##STR29## independently of one another are in the 3- or 4-position of the benzene ring, X represents hydrogen or --COR₂ where R₂is alkoxy of 1 to 4 carbon atoms, and A represents the radical of theformula ##STR30##
 3. A crosslinkable compound according to claim 1wherein A is --CH═CH--.
 4. A crosslinkable compound according to claim 1wherein A represents the radical ##STR31## X represents a --COR₂ group,where R₂ is alkoxy of 1 to 4 carbon atoms, or hydrogen, with the tworadicals ##STR32## in formula Ia' each being in the 3- or 4- position ofthe benzene ring.
 5. A crosslinkable compound according to claim 1 whichis ##STR33##
 6. A crosslinkable compound according to claim 1 which is##STR34##
 7. A crosslinkable compound according to claim 1 which is##STR35##
 8. A crosslinkable compound according to claim 1 which is##STR36##
 9. A crosslinkable compound according to claim 1 which is##STR37##
 10. A crosslinkable compound according to claim 1 which is##STR38##